I. Field of the Present Invention
This invention relates generally to acoustical barriers and more particularly to such a barrier mounted in an automobile between a body panel having an opening in which a speaker is suspended and a contiguous trim panel having a coaxial opening.
II. Background Art
Speakers produce sound by converting electrical energy into mechanical energy in the form of pressure waves hereinafter called sound waves. These waves are often created by the vibrating movement of a speaker cone, electrostatic panel, or the like. The speaker's vibrating surface typically has a face side and a rear side. The face side is designed to produce the audible sound that a listener hears and is placed in a mounting such that it directs sound waves toward the listening area. The rear side of the speaker's vibrating surface is on the other side or on the back of the face side. When the speaker is functioning, sound waves are generated on both the face side and the rear side of the speaker's vibrating member surface. Some cancellation of sound waves occur when waves generated on one side of the speaker's vibrating member are reflected to collide with waves generated on the other side of the speaker's vibrating member. This cancellation results in loss of certain frequencies and poor sound quality.
Speakers are mounted in automobiles in a number of ways. Typically, vibrating cone speakers extend through an opening in an automobile body panel so that the face is flush with the body panel. These speakers have a housing that includes radially extending mounting tabs having mounting apertures which register with mounting apertures in the body panel at the periphery of the body panel opening. Bolts are usually inserted through the registering apertures in the speaker housing and the periphery of the body panel opening and then fastened in place by nuts. In addition, a trim panel often covers the mounting panel for appearance sake and the trim panel must be provided with a corresponding opening to emit sound waves to the interior of the passenger compartment. Typically, the trim panel is spaced apart from the body panel and a portion of the sound waves are thereby emitted into the interspace between the panels. These sound waves can then be reflected by the panels and interfere with the sound waves emitted through the trim panel opening. The trim panel opening is often covered by a grill for the sake of appearance.
It has also been known to specially construct the speaker with a rigid grill housing that extends upwardly from the mounting panel to direct the sound waves from the speaker face through the trim panel opening. However, as frequently occurs, trim panels and body panels often have irregular surfaces or oversize openings. Furthermore, the trim panel is often spaced apart from the associated body panel such that both panels move relative to one another in a vibrating manner during operation of the automobile. Moreover, the distance between the panels can vary between different models of vehicles and even in different vehicles of the same model due to weather conditions, installation procedures, and the like. The previously known speaker housings are not well adapted to accommodate this wide range of panel variations. As a result, sound waves emitted from the rear side of the speaker can still collide with sound waves emitted from the speaker face, and can adversely affect the sound quality within the vehicle passenger compartment. Also, sound waves that reverberate between the two panels can escape through the opening in the trim panel and collide with sound waves emitted through the speaker grill. These conditions result in poor sound quality.